<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    
</body>
<script>
    // var age = 10;
    // var _age = "10";
    // var $age = 10;

    // alert(age == _age);//ture
    // alert(age ===_age);//false
    // alert(age ===$age);//ture


    //类型转换 - 其他类型转为数字
    alert(parseInt("12"));//12 parseInt 把字符串转为数字
    alert(parseInt("12B46"));//12
    alert(parseInt("B78"));//NaN (not a number)
</script>
</html>